1. Field of the Invention
The present invention relates to a magnetic recording apparatus and a magnetic reproducing apparatus capable of a search for record data according to for example a time code, such as DAT, 8 mm VTR, and digital video VTR.
2. Description of the Related Art
In an apparatus such as an 8 mm VTR and a video tape recorder performing record/reproduction of information on a magnetic tape with a rotating head, the rotating head achieves the record/reproduction by abutting on the magnetic tape in the direction oblique to the length of the magnetic tape and forming oblique tracks on the magnetic tape.
FIG. 5(a) and FIG. 5(b) are diagrams showing a pattern of record tracks scanned by a VTR of a helical scan type in the normal reproduction and a waveform of an RF signal output from the VTR, in which A1 to A4 denote tracks with data of odd-numbered frames recorded therein scanned by a first rotating magnetic head, while B1 to B4 denote tracks with data of even-numbered frames recorded therein scanned by a second rotating magnetic head, and these tracks are formed in a direction oblique to the length of the magnetic tape.
The arrow R indicates the rotating direction of a rotating head provided with a pair of reproduce heads, not shown, and the arrow F indicates the traveling direction of the magnetic tape.
In this case, the rotating head makes a scan by sequentially abutting on the loci of the record tracks A1 to A4 and B1 to B4, and, thereby, the pair of reproduce heads read the recorded data and output an RF signal as shown in the waveform chart of FIG. 5(b).
FIG. 5(c) and FIG. 5(d) are diagrams corresponding to the above described FIG. 5(a) and FIG. 5(b) when varying-speed reproduction, such as triple-speed reproduction, is performed, in which H denotes a rotating head having a pair of reproduce heads C and D. In this case, the traveling speed of the magnetic tape is increased and, on account of its relationship with the rotating speed of the rotating head H, reading of tracks is performed skippingly. Further, the angle of abutment of the rotating head H on the magnetic tape becomes acute, and, hence, the surface of its abutment on the record track decreases and its shifting to the adjoining record track becomes faster.
Then, the data recorded in the tracks A1, B2, A4 disposed at intervals come to be output and the output RF waveform becomes as shown in a waveform chart of FIG. 5(d), that is, an RF signal in which data are not continuous from track to track is obtained.
When performing a high-speed search of programs or the like recorded in a magnetic tape or cuing, it is achieved by detecting a cuing signal, a time code, or the like recorded in a subcode area provided in a predetermined position of the record track.
FIG. 2 is a diagram showing an example of format of the subcode formed at a portion of the record track.
The subcode, as shown in FIG. 2(a), is formed of a preamble portion, a data portion, and a postamble portion. The data portion, in the case of this example, is divided, as shown in the diagram, into 12 sync blocks SB1 to SB12, which are properly used for three kinds of data, with the same data repeated four times.
FIG. 2(b) is a diagram showing data within one sync block of the data portion in an enlarged scale.
In this diagram, there are provided, in succession to a sync area SYNC, header areas W1 and W2 of the subcode, in which such data as the above mentioned cuing signal are recorded. The sync block further has a parity P of the header areas W1 and W2, a data area of the subcode with the above mentioned time code and the like recorded therein, and a parity C1 of the data area. Incidentally, a graduation shown in FIG. 2(b) indicates a length of one byte.
When a high-speed search at for example hundred-fold speed or above is performed on a tape with such a subcode recorded therein, then, what can be read is the data recorded in only a part of tracks, as was the case with the increased-speed reproduction described in FIG. 5(c) and FIG. 5(d), Hence, it becomes difficult to read the data in seven bytes in all including the parity C1. Thus, there has been a problem that it is thereby made difficult to read the time code for making a search for a position where the tape is to be stopped or to make cuing.
It is an object of the present invention to provide a magnetic recording apparatus and a magnetic reproducing apparatus capable of solving the above mentioned problem. In order to achieve this object, the present invention is adapted, by using, in the recording mode, generation means for generating address information of record data in absolute address and its time code, record means for recording a first time code in hour-minute-second units in a data portion of the subcode formed in the track, and record means for recording a second time code in hour-minute units, being high-order data of the first time code, in a header portion of the subcode in the record data format, to record the time codes, together with record data, in a magnetic tape.
In making a high-speed search for the contents recorded in the magnetic tape, the present invention is adapted, using detection means for detecting a first time code in hour-minute-second units recorded in a data portion of the subcode formed in the track and detection means for detecting a second time code in hour-minute units, being high-order data of the first time code, recorded in a header portion of the subcode in the record data format, to perform a high-speed search from the start to a predetermined position according to the second time code in hour-minute units recorded in the header portion of the subcode and perform a reduced-speed search from the predetermined position to the desired position according to the first time code in hour-minute-second units recorded in a data portion of the subcode.
Since the time code in hour-minute units is recorded in the header portion of the subcode in the magnetic tape, it is made possible to detect the elapsed time in units of minutes even while a search is being made at high speed, and thus a superhigh-speed search can be carried out.